Walls in the city incorporate many eamples of ownership stones, boundary markers, and (usually) undecipherable stones or bricks giving initials only.
This one can be hard to find amongst growing foliage in spring and summer months. Most of it (not all) is clearly legible - see transcription below:
THIS TABLET MARKS THE
WEST WALL OF THE ANCIENT
CHURCH OF ST MARY QUENINGATE
& THE STONE IN THE GRA..*
THE RETURN OF THE
* apparently 'the stone in the grass'
click to enlarge and read caption
© Geoff Downer 2019